If you were obviously jamming a single finger in the neck. Would that be frowned upon? I normally do fist or elbow or knee or something.
There is a neck grab where you latch on to the muscle at the side and kind of roll it forward. Or even slapped on collar ties.
Well, in this case, is a finger behind the ear connection with the jaw, during the movement to make a takedown, it hurts as fk and can be considered illegal.
btw the video just proves what I said, just because is rare and not mainstream isn't proof of ineffectiveness.
See videos of ppl fighting on the street and talk more about how popular the art is instead of how effective is.
And once more, For use a tech from a martial art you don't need to be in the kamae (guard) of the martial art like a martial art dummy, especially if you are training in Bujinkan is a recurrent theme the Hatsumi says to lose the kamae and adapt the tech to yourself.
More one thing, for example, Tachi nage if you see in MMA you will say is judo, but can also be from Bujinkan and when you are fighting with a stance like anyone else you will never notice from where it came from. Another example is Mawashi Geri karate is the same as round kick and is the same as dollyeo chagi teakowondo, if the person is fighting you will never know from which art it came from, cuz this I repeat Rokas don't understand fighting and much less data interpretation.
Fighting has a sweet spot to jiu Jitsu, to kickboxing, to aikido and etc work anyone who fights constantly knows, is not A or B doesn't work is more about our own judgment that is unreal in terms of timing.
just to add
Enson Inoue was a black belt in bujinkan and bjj and a really good old school mma figther.